It is known that the external tensile stresses or compressive stresses necessary for maintaining the plastic deformation of metallic materials can be significantly reduced by macrosonics of sufficiently large intensity. See the following literature: F. Blaha and B. Langenecker "Dehnung von Zink-Kristallen unter Ultraschalleinwirkung"; die Naturwissenschaften, 20, 556 and 557 (1955) and B. Langenecker, C. W. Fountain and V. O. Jones, "Ultrasonics: An Aid to Metal Forming?"; Metal Progress (1964). This fact opens up possibilities of use in the metal working industry. Several patented methods and devices are based on this effect of the reduction or decrease of the external forming forces by ultrasonics acting on the material (see U.S. Pat. Nos. 2,638,207, No. 2,568,303 and Austrian Pat. No. 246,082). These patents, in turn, in their conception, go back to the arrangement disclosed in the aforementioned publications.
The ultrasonics which comes into action is generated in a converter (transducer) by transforming electrical signals into mechanical oscillations and is amplified in a horn which oscillates in the direction of its longitudinal axis. As a rule, the drawing die is arranged in one of the displacement antinode of the ultrasonically oscillating horn, where the deformation of the wire takes place. In the following, the term wire also means rods, tubes, pipes, profile wire and the like. Only in Austrian Pat. No. 246,082 is the drawing die (nozzle) arranged in the nodal point, that is, in the stress antinode of the horn which is exited to a standing ultrasonic wave.
All these and similar methods and arrangements are only particularly effective at drawing speeds which are not larger than about the velocity of particle displacement. The term velocity of particle displacement v, of a sound field refers to the periodically changing velocity of the oscillating particles with reference to space and time. This velocity is measured in the usual speed dimension: ##EQU1## wherein A is the amplitude, .omega. is the angular frequency and c is the velocity of sound.
It follows that significant effects of macrosonics on the metal plasticity are rendered possible with the hitherto common frequencies of less than 100 kHz--usually 20 to 30 kHz--at drawing speeds below several meters per second. Since in industrial practice, materials which are difficult to deform, for example, molybdenum, tungsten, and others, are conventionally drawn substantially slower, without the use of macrosonics, than that corresponding to the velocity of particle displacement, in all these cases the activity of macrosonics according to the methods and devices referred to allows for significant possibilities for increasing the drawing velocities and also renders it substantially possible to increase the area reduction per drawing stage, as compared to the hitherto common conventional wire drawing procedures. In this manner, the productivity of the ordinary common wire drawing procedures is significantly increased.
Moreover, it is also possible to produce wires from such materials which, with the presently common conventional methods, either cannot be drawn at all or can be drawn only by also supplying heat (by heating the wire). The heating of the wires, however, results in the fact that the characteristics of the material may be negatively influenced by the thermal effect and this makes it sometimes necessary to perform a suitable after-treatment in order to again obtain or to attain the desired characteristics of the wire.
The macrosonic drawing procedure also permits the heating of such wires made of materials which cannot be drawn at all at room temperature or only can be drawn with great difficulty, so that it is then possible with the action of macrosonics to draw at room temperature. With several materials, for example, highly alloyed steel wires, the otherwise necessary chemical pre- and post-treatments can be dispensed with, which treatments are otherwise necessary for protecting the material with respect to the thermal treatment, or which have to be used in conventional procedures if the lubricant does not adhere to the material as soon as the wire is drawn through the drawing nozzle. The macrosonic procedure thus offers, in addition to increase of productivity, savings in that heating and chemical pre- and post-treatments can be dispensed with when compared with the conventional processes. This applies, for example, to the treatment referred to as "bonderizing".
The above statements, in the sense of the above-mentioned limitation of the velocity of particle displacement, relate to deformation speeds which are below several meters per second. With increasing deformation speed, to wit, if one, from a magnitude point of view, deforms in a manner equal to the size of the velocity of particle displacement, and still more rapidly, then the above-mentioned effect of the macrosonics decreases appreciatively on the metal plasticity until this effect finally, at very high speeds, disappears entirely.